SCSS Generation Error

[TheBrambleShark]

Initially I thought this may have been an issue with the SCSS library I was using (imperavi/superkube#8), however the fact that I have left this project alone since I made that issue and today I tried picking it up again and received a different error tells me something else may be going on.

I am targeting .NET 6 and I have these includes:

<ItemGroup>
  <PackageReference Include="Microsoft.AspNetCore.Razor" Version="2.2.0" />
  <PackageReference Include="Statiq.Web" Version="1.0.0-beta.41" />
</ItemGroup>

The nature of the issue seems to be consistent, but which mixin it fails to find seems to change based on the day. Currently, it's this:

Error: no mixin named placeholder
        on line 20 of input/assets/lib/superkube/base/elements.scss
>> @include placeholder(var(--placeholder-default));

   ---------^

This seems to be a cascading variable because anything after the line in question also fails every other include. Any ideas where to start debugging this?